A long time ago, the kinds of animals we now have as pets were once untamed creatures.

But did you know that some pets have gone back to the wild?

These once-domesticated animals escaped from their homes or were let go by their owners. Some of them formed packs or flocks and had babies that never lived in captivity. This is how they became wild animals again.

Here are some of their stories:

Snakes on vacation

If you were in Florida and saw a Burmese python slither by, the first thing you might think is, "Help, a snake!"

But you should also be surprised because Burmese pythons aren't American snakes; they're native to Asia. So what are they doing in Florida?

Well, people probably bought these snakes as pets when they were cute, little babies. When they grow into 15-foot-long eating machines, though, owners have sometimes set them free in the Everglades, a wetlands area in the southern part of the Sunshine State.

The Burmese python, which can weigh up to 250 pounds, swallows its prey whole in one gulp and can strangle an alligator, but not if the alligator eats the snake first!

The Everglades have turned out to be python heaven because of the tropical climate, which pythons like, and also because there's plenty of food, such as deer. But the best part for the snakes is what's missing: the predators that eat the pythons in their native habitat.

What's good for the snakes is bad for the native animals of Florida, though, and also for the people who live there. Biologists estimate that there are 30,000 nonnative giant snakes living in the Everglades – and some of them have made their way to other parts of Florida and even to other states.